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Top Balancing using SI-6048?

Disturbedfuel15

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Aug 12, 2023
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Hello,

It appears I pulled a rookie-move and had my JK PB2A16s20p balancing turned on when the cells were at 70%, where they came from the factory. I didn't realize I was possibly doing harm... now I know. In any case, I have five of these BMS, five 48v 280ah packs. The cells are laser-welded together, so I cannot remove them and connect all batteries in parallel to pursue the recommended top balance settings. I'm also using two SI6048US on the latest firmware. They are talking to the BMS pretty well for the most part. I have the battery type as external lithium ion, so it gets all charging parameters from the BMS (I believe).

There are a few cells in a couple packs that charge faster than others, causing the charging to stop due to cell OVP.

What I've read is that nowadays with active balancers, like these have, with 2a balancing current, I may be able to top balance by just letting the BMS' do their thing. I don't know that I can make the SIs send a constant charge voltage, so I have a 10a 0-60v bench power supply coming, too. If I don't have to open it and I can return it, that would be terrific. I'd like to top balance using the SIs.

I'll post my current BMS settings here. The only difference I made this morning before posting is I upped the requested charge voltage to 3.5v from 3.45v, and I set the charge current max at 2.0a in hopes the cells don't drift too far apart under this smaller charge current. Looking at the BMS displays currently, I'm seeing between 1-2a of current, so the BMS are doing their job. Once all cells reach 3.5v and are within .0010v of eachother, I want to up it to 3.55v, then 3.6v, and then maybe call it good? How does that sound? I appreciate any responses tremendously. I'm here to learn. Thank you!

Screenshot_20240504_110659_BMS.jpg
 
I did a top balance with a JK-PB2a and an SMA SI5048 using SI6048US firmware and running closed loop Canbus, it was down to 0.002V deviation between cells yesterday..

Balance on is set to 3.45V,

Vol cell RCV 3.513

SOC-100% Volt 3.512

Cell OPRV 3.498.

Reason for the higher Vol Cell RCV is that the SI5048 takes off 1V from the Canbus info sent to it by the JK and reports it as 55.2V for the 16 cell bank instead of 56.2.

So your 3.5V is not getting through to the SI as 56V but as 55V

All detailed in this thread

 
I'll add the current status of each 16s bank here. Now that I look at it, it seems everything cell is already pretty close, perhaps this 2a limit helped. Maybe it's when charging at 30a+ that it caused certain cells to charge faster. Anyway, in the future, I'm planning many cycles for these and I can't have that happen when charging at full capacity. I believe that means I still need to continue to top balance, albeit with a higher voltage already? 3.55v? It also seems like the biggest delta is between packs, not between cells.
20240504_111517.jpg20240504_111536.jpg20240504_111512.jpg20240504_111530.jpg20240504_111524.jpg
 
I did a top balance with a JK-PB2a and an SMA SI5048 using SI6048US firmware and running closed loop Canbus, it was down to 0.002V deviation between cells yesterday..

Balance on is set to 3.45V,

Vol cell RCV 3.513

SOC-100% Volt 3.512

Cell OPRV 3.498.

Reason for the higher Vol Cell RCV is that the SI5048 takes off 1V from the Canbus info sent to it by the JK and reports it as 55.2V for the 16 cell bank instead of 56.2.

So your 3.5V is not getting through to the SI as 56V but as 55V

All detailed in this thread

Thanks, I will try those parameters. It does seem I need to put the SI in standby before adjusting, or else it gets confused and shuts off when adjusting each BMS, no matter how quickly I try to adjust the RCV/etc. No big deal, just an observation I found. Thanks again.
 
Have you calibrated the voltage of each BMS, mine were not matching the SI but the digital meter was spot on to the SI so I calibrated to the digital meter when the battery was resting.

Calibrating the amps should be b=done under load but not really got that sorted yet, it goes off as the load drops and shows too much discharge overnight at low loads compared to the shunt linked to the SI.
 
I did a top balance with a JK-PB2a and an SMA SI5048 using SI6048US firmware and running closed loop Canbus, it was down to 0.002V deviation between cells yesterday..

Balance on is set to 3.45V,

Vol cell RCV 3.513

SOC-100% Volt 3.512

Cell OPRV 3.498.

Reason for the higher Vol Cell RCV is that the SI5048 takes off 1V from the Canbus info sent to it by the JK and reports it as 55.2V for the 16 cell bank instead of 56.2.

So your 3.5V is not getting through to the SI as 56V but as 55V

All detailed in this thread

Sorry for double quoting, but do you perhaps think that is a problem with 5048 and not the 6048? From Data Manager M Lite:
1714836726336.png
 
Thanks, I will try those parameters. It does seem I need to put the SI in standby before adjusting, or else it gets confused and shuts off when adjusting each BMS, no matter how quickly I try to adjust the RCV/etc. No big deal, just an observation I found. Thanks again.
I have yet to see that, even changing from one of the 3 working canbus protocols to another working one shows no glitches and the SI carries on.
 
Have you calibrated the voltage of each BMS, mine were not matching the SI but the digital meter was spot on to the SI so I calibrated to the digital meter when the battery was resting.

Calibrating the amps should be b=done under load but not really got that sorted yet, it goes off as the load drops and shows too much discharge overnight at low loads compared to the shunt linked to the SI.
I did not calibrate the voltage of each BMS. I did not know I had to do that and I do not know how to do that.
 
I will still set the SOC100/etc values to .001 lower than the previous, like I would have it if I were not top balancing. I didn't know how the SI would handle the RCV being .5v higher than the SOC100%. Let's see what difference that makes.
 
Mine is
I did not calibrate the voltage of each BMS. I did not know I had to do that and I do not know how to do that.
Easy, its on the 2nd page of the Windows/Bluetooth app. Look for Basic settings at the top of the page.

Calibrating Volts and next to that is the current volts it thinks the bank of 16 cells in total is.

Take an accurate meter and measure the bank volts at the 2 +/- lugs, then put that voltage in overwriting the current measurement. The voltage on the first page will change and all the 16 cell voltages changed to add up to the calibrated Volts.
 
You calibrate the Amps in the same way but under a heavy charge and using a DC clamp meter.
 
Post picks while they are still charging at the top voltage. All the packs should be at the same voltage, and cell delta under .010v
 
I will still set the SOC100/etc values to .001 lower than the previous, like I would have it if I were not top balancing. I didn't know how the SI would handle the RCV being .5v higher than the SOC100%. Let's see what difference that makes.
I suspect that SOC 100% voltage will trigger the SI to reduce the charge, I have always had it 0.001V below the RCV so have not tried it so its a guess. Next sunny day I will test to see.
 
Mine is

Easy, its on the 2nd page of the Windows/Bluetooth app. Look for Basic settings at the top of the page.

Calibrating Volts and next to that is the current volts it thinks the bank of 16 cells in total is.

Take an accurate meter and measure the bank volts at the 2 +/- lugs, then put that voltage in overwriting the current measurement. The voltage on the first page will change and all the 16 cell voltages changed to add up to the calibrated Volts.
I honestly did not know this was a thing. I had no idea what it did. Thank you for this. It is easy and I will do it now. I also have a fluke clamp meter if I need to do the amp calibration in the future....
 
Disable comms until you have it all top balanced.
I suspect this would mean reconfiguring the battery type in the SI as lead acid. I'd have to do research on this, as I did not delve into the lead-acid structure. Are you sure this is necessary? If BMS controls the charge, couldn't I use the BMS to request whatever I want from the inverter? Thanks for your help!
 
I would calibrate the voltage for each pack, then see how close they are. I suspect they will be close enough they will top balance without resetting the SI.
 
I would calibrate the voltage for each pack, then see how close they are. I suspect they will be close enough they will top balance without resetting the SI.
WOW! They are all the exact same voltage! I made sure to disable charge/discharge before measuring each one. You've once again saved me a lot of time, thanks.

I think I'm going to go ahead and up the RCV again and let them continue to do their thing.
 
I suspect this would mean reconfiguring the battery type in the SI as lead acid. I'd have to do research on this, as I did not delve into the lead-acid structure. Are you sure this is necessary? If BMS controls the charge, couldn't I use the BMS to request whatever I want from the inverter? Thanks for your help!
What you want to do is charge until bms cuts out.
Hold voltage under the cutoff as cells balance.
Slowly increase in 0.1v increments until you reach 57.6v, or bms limit.

Can't do that with bms controlling.

Then your cells will be balanced. Bms cutting out prevents cells from really balancing.
 
Leave it 24 hrs and then see what the cell delta is for each battery. Your worst battery pack is currently at 10mv delta, no need for a top balance if tomorrow you see the same or even slightly worse. Just setting balance at 3.45v will keep them on target. Its a pain telling the SI to go back to acid and then back to Lithium and having to reset the shunt setting every time.
 
Right now I have the RCV at 3.6 and they are all sitting at just about the same as pictured:
20240504_134329.jpg
I feel like I should go to 3.64, and if they are still good once current reaches 0, call it balanced?
 
I don't see the point of going above 3.6V unless you are planning a capacity test. They are still balancing at 3.5875V, let them do their thing. This was why I went for this BMS, active balancing at 2A.
 
I don't see the point of going above 3.6V unless you are planning a capacity test. They are still balancing at 3.5875V, let them do their thing. This was why I went for this BMS, active balancing at 2A.
Aha! I think I found something after calibrating the BMS voltage. I needed to increase each one by about .2v to get it correct with what the actual voltage was. No current is flowing right now, even though they aren't at 57.6v--they are currently at 57.4v and nothing is changing. I looked at the data from SI and it reports the voltage is 57.6v. The SI is now .2v > the actual calibrated voltage. Hmmmmm makes me wonder.

The BMS should be reporting real time data to the SI. However, I wonder if the newly calibrated BMS voltage values being sent to the SI never got updated? In this case, I wonder if power cycling the SI or the BMS would cause the voltages to fall in line == ? I do know one thing, nothing is happening right now. They are all sitting at the same exact readings I posted earlier.

Oh, one more thing. I thought I had posted this, but I guess I did not.
I found a setting that allows you to limit the charge current, so I have that set on the SI as well as the BMS (already knew about BMS). I have it set to 10a, 2a per pack while 'top balancing':
1714848658353.png
 
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Assume you have one BMS set as 1 on the dip switch and the rest as 2, 3, 4 etc, so 1 is the only BMS sending canbus messages to the SI, check the RCV it's set to and compare it to the SI. It may need the SI to be put to standby and restarted.
 
Assume you have one BMS set as 1 on the dip switch and the rest as 2, 3, 4 etc, so 1 is the only BMS sending canbus messages to the SI, check the RCV it's set to and compare it to the SI. It may need the SI to be put to standby and restarted.
Yeah, I think I'm going to do that. And actually you are correct, but technically I have the first DIP switch on 0, with 1, 2, 3, 4 following. If I started at 1, there were no communications! Really it seems JK has left it up to the community to find out how to use these.

Either way, it seems my cells are balanced... they are all within 0.010 of each other, every cell, every pack, while sitting charged at 57.7v (3.603/cell). I know it seems like it did not take long, but I have had them up and RCV of 3.45, balancing at 3.4 for a couple days before this. Unless someone feels differently, I think these are top balanced. I'm far from an expert, however.

I went off of the forum's Top Balance Tutorial, Appendix D: Top Balance using an active balancer:
"Once a cell reaches 3.45 volts during a charge cycle, turn the active balancer on and let it actively balance till all the cells are fully charged. This works best if the charge current is low. Otherwise the charge current overwhelms the balance current and one of the cells can still ‘run away’. One good way to prevent this is to start with a reasonably low charge voltage like 3.5V/cell (14V pack voltage for a 12 V system) and low charge current (1 or 2 amps) and let it go till the cells are all balanced. Then step the voltage up a bit and let it repeat. Keep doing this till the voltage reaches 3.6V/cell and the current drops off to near zero."
 
Still only got one battery/BMS, parts for second are on route. I have mine set as 1, only setting I can get RS485 to work so assumed that would work for setting up 2nd battery. Then after 2nd battery was set up it would be set to 2 and linked to 1. Will have to try 0 tomorrow.
 
Set my BMS to 0 on Dip switches, windows software connects but goes straight to parallel tab showing real time data for multiple batteries but as I only have one the rest show as disconnected and cannot get access to any of the other tabs as they are greyed out. If you select device 0 when connecting it changes to device 1 when you connect which is not what the dip switches are set to.

Bluetooth App connects and you can go into settings and change them, Device ID shows as 0.

So totally confusing, to change the settings using the Windows app you need to set the dip switch to 1, only then can you change settings and upload new firmware. To get the batteries to have comms between batteries you set one battery to 0 and the rest as 1, 2 etc.
 
Set my BMS to 0 on Dip switches, windows software connects but goes straight to parallel tab showing real time data for multiple batteries but as I only have one the rest show as disconnected and cannot get access to any of the other tabs as they are greyed out. If you select device 0 when connecting it changes to device 1 when you connect which is not what the dip switches are set to.

Bluetooth App connects and you can go into settings and change them, Device ID shows as 0.

So totally confusing, to change the settings using the Windows app you need to set the dip switch to 1, only then can you change settings and upload new firmware. To get the batteries to have comms between batteries you set one battery to 0 and the rest as 1, 2 etc.
What odd behavior, but not unexpected. You know, I have five of the old reliable b-series jk bmses. I wanted them on hand in case this didn't work. I'll probably be selling them soon it seems because I am happy with the functionality of these, although I am scared to death to do any updates now on both the SI or the BMS. I don't want to break anything!

I am curious what RJ45 port you are using to connect to the BMS? Reason I ask is to eliminate all variables between your experience and mine. I'll be curious once you get anther BMS in. Here is where I did firmware update/connected to PC: https://diysolarforum.com/threads/jk-pb2a16s-20p-no-communication.78801/post-1010240

I completely reset my sunny islands, setup as new systems. I was hoping it would fix the SOC being stuck at 99% and the batteries forever-charging. It did go to 100% for a bit, but it's back at 99% and it is holding the packs at 55.2v (RCV 3.45v*16). I do not believe it is healthy for the cells to stay at this voltage. I would like them to be released and brought down to float voltage, 3.35. I do not know how to accomplish this.

However, I found a parameter that may get me by for now:
Lmt battery state of charge for connection to grid (GdSocTm1Str) Could set this to 95% so grid disconnects once battery SOC is 95%
Lmt battery state of charge for connection to grid (GdSocTm1Str) Could set this to 40% so grid connects once battery SOC is 40%

Keep in mind I do not have any PV setup yet. Just battery backup right now. I'm not sure if it would do what I want, but I'm trying to figure something out.
 
I am PV only and off grid so can't answer you on grid queries.

The ports that work with the Windows App are two marked RS485-2, these are the greyed out Uart-2 in the app that are fixed to JK-BMS RJ45 Modbus V1.0. So one can be used to connect to PC and 2nd to next battery.

To drop your charge voltage use the app to change the RCV from 3.45V to your preferred lower V 3.35V, I can leave mine at 55.2V as using PV it takes until 3 or 4pm before I get there and then the sun intensity drops so the voltage drops naturally. The float function volts settimgs in the BMS does not get to the SI so until that is fixed you need to change the RCV using the app.

I have an HiFlying Elfin EW11 connected to the RS485 port on the BMS to send the data to my Wifi and then use a virtual serial port on my PC 25 yds away to connect to the JK so I can change settings in comfort.

I am on Firmware 15.17, if further updates come that break functionality you can force a firmware upgrade to an earlier working firmware but you need an added code which you get from here.

https://mirofromdiro.github.io/JK-firmware-code/
 
I am PV only and off grid so can't answer you on grid queries.

The ports that work with the Windows App are two marked RS485-2, these are the greyed out Uart-2 in the app that are fixed to JK-BMS RJ45 Modbus V1.0. So one can be used to connect to PC and 2nd to next battery.

To drop your charge voltage use the app to change the RCV from 3.45V to your preferred lower V 3.35V, I can leave mine at 55.2V as using PV it takes until 3 or 4pm before I get there and then the sun intensity drops so the voltage drops naturally. The float function volts settimgs in the BMS does not get to the SI so until that is fixed you need to change the RCV using the app.

I have an HiFlying Elfin EW11 connected to the RS485 port on the BMS to send the data to my Wifi and then use a virtual serial port on my PC 25 yds away to connect to the JK so I can change settings in comfort.

I am on Firmware 15.17, if further updates come that break functionality you can force a firmware upgrade to an earlier working firmware but you need an added code which you get from here.

https://mirofromdiro.github.io/JK-firmware-code/
When setting the RCV last night, I accidentally hit the "li-ion" button, which immediately applies all default parameters for lithium ion without any other confirmation. One slip and you're done.

Well, I got all the settings back to where they were before. Now bms is showing 69% charge. The aggregate SOC sent to SI is now 92%. I really hate the design of these bms. That one slip of my finger just screwed up the entire system. I'm not sure how to get it back to 100%, like the rest. Obviously it is 100%... The BMS is just miscalculating. Frustrated with these bms for sure.
 
It will jump to 100% once it hits the RCV, to get it higher than it is now, but it wont be 100%, then start charging and when the voltage climb levels off then change the capacity by 1ah.
 
Thanks for the advice. I figured out it will reset to 100% once it hits the SOC 100% setting. Older BMS did not have this setting. So I set the RCV to 3.5, let the battery hit the SOC100% and now it is back at 100%. Now I will float at 3.4. I am wondering how often I need to charge at absorption voltage, or if I can just leave it at 3.4 for extended periods of time. Reason being, I'm hooking up my critical loads panel, and the batteries will get used. Therefore, do I only want them charging to 3.4 after use or do I need to manually change the RCV from absorption to float every time I charge the batteries? I am not sure how often I need to charge at absorption voltage. I need to read more about it.
 
Until the float function works via the Canbus comms if you need a float V and an adsorption V then you need to be changing the RCV to suit. As to whether a set of well balanced cells needs a period of absorption is not something I have looked into, being PV charged I get that by default anyway every day I get the batteries to 100%. Going by the weather this week its not going to happen for a few days and I have no concerns and the cell delta is staying well under .010V. I think its more important to have the info and be able to change the settings if you see the cell delta go out of line
 
I can confirm that Float works, had a really sunny day and the battery was at 55.2V for some time and then the target voltage on the SMA dropped to 53.6V which is -1V from the JK float setting Vol RFV I have of 3.415. I have an RCV time set of 1H so that must have elapsed and the float started.

This was using Deye Canbus on the JK, not sure of the significance.
 
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